Pelvic organ prolapse (POP) reduces the quality of life of many older women in the U.S. There is an unmet need for non-surgical therapies based on POP pathophysiology, to prevent and/or regress this common condition. Towards pioneering the development of such a therapy, we propose an exploratory study to (a) assess aberrations of the structural extracellular matrix (ECM) as a pathophysiological basis for POP and (b) establish proof of concept of an innovative therapeutic strategy based on induced regenerative extracellular matrix repair. Recent data in humans and lysyl oxidase like protein-1 (LOXL1) knockout (KO) suggest that impaired ECM remodeling, particularly that of elastic matrix may be linked to POP. However, it is not known if decreased LOXL1 and aberrations of ECM homeostasis, occur in all POP patients, and if they are a cause of POP or a result of it. Since vaginal wall ECM mechanically supports pelvic floor tissues, restoring homeostasis of vaginal ECM in post-partum pelvic floor tissues may be an effective approach to prevent or reverse POP symptoms even though the clinical etiology may be varied and multifactorial. Elastic matrix does not usually regenerate well in adult tissues and will therefore be our primary target for regenerative therapy, although we will assess restoration of collagen homeostasis as well. We propose to utilize a LOXL1 knockout (KO) mouse model of POP to perform a first phase correlative study to elucidate these mechanistic aspects that, beyond this study, will be useful to assess in vivo therapeutic efficacy of our matrix regenerative approach. We propose two aims to test our hypotheses that LOXL1 deficiency results in aberrations in vaginal ECM assembly & repair after pup delivery, which together with enhanced matrix degradation are associated with POP, and that these aberrations can be attenuated or reversed by induced cellular regenerative ECM repair. Aim 1a. Determine the time course of changes to the homeostasis of structural ECM of the vaginal wall corresponding to POP in LOXL1 KO mice. Aim 1b. Determine how LOXL1 deficiency, pregnancy, vaginal delivery, and prolapse in LOXL1 KO mice, alter new ECM deposition by Non-Epithelial Vaginal Cells (NEVCs). Aim 2. Assess ability of MRFs to restore indicators of structural ECM homeostasis in organ cultures of vaginal wall tissue isolated from LOXL1 KO mice with and without POP. The proposed project builds on an ongoing collaboration and expertise of the co-PIs, Damaser (animal models and POP pathophysiology) and Ramamurthi (ECM regeneration). The study will provide justification, rationale, and feasibility data to continue development of this paradigm-shifting, minimally invasive regenerative therapy with pre-clinical studies in animal models and cultured human vaginal tissue. These in turn will rationalize clinical trials to prevent and/or treat POP towards improvin quality of life for many women. The scientific impact of this study will be improved understanding of the mechanisms of POP development and testing of an innovative therapy for regenerative elastic matrix repair and restoration of ECM homeostasis.